French police were involved in a prolonged shootout in the northern Paris suburb of Saint-Denis early on Wednesday, where a Belgian Islamic State militant suspected of masterminding last week's Paris attacks was believed to be holed up.

Police and justice sources said Abdelhamid Abaaoud, 27, thought to have pulled the strings from Syria, was strongly believed to be among a group of people holed up in an apartment in the northern suburb near the national soccer stadium, one of the sites attacked by suicide bombers last week.

Shooting began at about 4.30 a.m. (0330 GMT) and police special forces of the RAID unit were still involved in exchanges of fire three hours later, witnesses said.

A police source said three suspects had been arrested so far. A justice source said at least two had been killed, including a woman who blew herself up with a suicide belt.

The source said the operation was still under way shortly before 8 a.m. (0700 GMT) and police were still trying to "neutralise" two more suspects.

"There are men from RAID shooting from the rooftops," Djihane, a neighbour, said on France Inter radio. "We've been told to lie on the floor and not go to the windows."

Three policemen and one other person were hurt during the operation. There was no immediate official confirmation.

The operation took place near the Stade de France soccer stadium where three suicide bombers detonated their explosive belts and killed a passerby on Friday.

In all, at least 129 people died in Friday's attacks, which have been claimed by the Islamist militant group Islamic State. Seven militants died in the assault. Two are known to be on the run.

Earlier, two Air France flights en route to Paris from the United States were diverted because of security issues, the Federal Aviation Administration (FAA) said.

An Airbus A-380 that departed from Los Angeles landed in Salt Lake City, where passengers and crew were being deplaned and transferred to the terminal, an FAA spokesman said.

A separate flight that left Dulles International Airport outside Washington was diverted to Halifax International Airport in Nova Scotia also because of an unspecified security concern, the FAA said.